1. Field of the Invention
The present invention relates to a swivel joint for high pressure fluid to be used in leading high pressure fluid from a fixed body into a rotating body.
2. Description of the Background Art
As a conventional swivel joint for high pressure fluid to be used in leading high pressure fluid from a fixed body into a rotating body, there is a type of swivel joint which utilizes lubricant in order to increase sealing effect of the high pressure fluid and at a same time smoothing the rotation of the rotating body, such as those disclosed in Japanese Patent Application Laid Open No. S57-137792, Japanese Utility Model Application Laid Open No. 61-184188, and Japanese Utility Model Application Laid Open No. 61-184189.
In such a conventional swivel joint for high pressure fluid, in order to prevent the leakage of the high pressure fluid from a passage joining a fluid path inside the fixed body and a fluid path inside the rotating body, there is provided a packing between the fixed body and the rotating body and also a lubricant having the same pressure as the high pressure fluid is supplied externally to the packing on a side opposite to that facing the passage. Thus, in this swivel joint for high pressure fluid, the leakage of the high pressure fluid is prevented as a result of balancing between the pressures exerted to the packing from opposing sides, and at a same time the rotation of the rotating body is smoothed by the lubricant.
However, in such a conventional swivel joint for high pressure fluid, it has been necessary to provide a separate means for supplying the lubricant at an appropriate pressure, which usually comprises a cylinder incorporating a piston on one side of which a part of the high pressure fluid is led and on the other side of which the lubricant to be supplied is led, so that it has been unavoidable for a number of elements involved to become too great from a standpoint of compactification as well as that of manufacturing cost.